Embodiments of this application relate generally to light emitting devices and more specifically to emitting light in from an emitter confined between a semiconductor layer and a metallic structure.
Entire classes of materials are currently unsuitable for use as substrates in visible light emitting devices (LEDs) due to their optical properties. For LEDs operating at visible frequencies, silicon (Si), is an example of an unsuitable substrate. If LEDs could be formed directly on silicon, it would provide an interface between electronic signal processing in silicon and optical signal generation for data transmission or visualization. An advantage of using light at visible frequencies is that two common detectors, the human eye and silicon diodes, are highly-sensitive in this frequency regime.
Silicon, however, has a high index of refraction and is absorbing to light at visible frequencies. Thus, conventional LEDs on silicon are optically isolated from the bulk silicon substrate to prevent the emitted light from being guided into the silicon, where it would then be trapped and absorbed. In practice, this optical isolation typically requires the LED to be fabricated separately and then bonded or soldered onto the silicon.
Similar concerns restrict the development of LEDs on many high-index, absorbing materials in various frequency ranges in the visible and near-infrared, such as gallium phosphide, aluminum phosphide, aluminum arsenide, boron phosphide, boron arsenide, and germanium.